The use of a UAS (Unmanned Aircraft System) was tested to survey large mammals in the Nazinga Game Ranch in the south of Burkina Faso. The Gatewing ×100™ equipped with a Ricoh GR III camera was used to ... [more ▼]

The use of a UAS (Unmanned Aircraft System) was tested to survey large mammals in the Nazinga Game Ranch in the south of Burkina Faso. The Gatewing ×100™ equipped with a Ricoh GR III camera was used to test animal reaction as the UAS passed, and visibility on the images. No reaction was recorded as the UAS passed at a height of 100 m. Observations, made on a set of more than 7000 images, revealed that only elephants (Loxodonta africana) were easily visible while medium and small sized mammals were not. The easy observation of elephants allows experts to enumerate them on images acquired at a height of 100 m. We, therefore, implemented an aerial strip sample count along transects used for the annual wildlife foot count. A total of 34 elephants were recorded on 4 transects, each overflown twice. The elephant density was estimated at 2.47 elephants/km2 with a coefficient of variation (CV%) of 36.10%. The main drawback of our UAS was its low autonomy (45 min). Increased endurance of small UAS is required to replace manned aircraft survey of large areas (about 1000 km of transect per day vs 40 km for our UAS). The monitoring strategy should be adapted according to the sampling plan. Also, the UAS is as expensive as a second-hand light aircraft. However the logistic and flight implementation are easier, the running costs are lower and its use is safer. Technological evolution will make civil UAS more efficient, allowing them to compete with light aircraft for aerial wildlife surveys. [less ▲]

There is a lot of uncertainty in the amount and spatial variations of above-ground biomass in Africa, partly because very few allometric equations are available. The aim of this study was to assess the ... [more ▼]

There is a lot of uncertainty in the amount and spatial variations of above-ground biomass in Africa, partly because very few allometric equations are available. The aim of this study was to assess the validity of using pan-tropical multispecies allometric equations developed by Chave et al. (2005) for estimating the above-ground biomass of trees in Central Africa and/or to develop site-specific equations. The study was conducted in lowland tropical forests of South-eastern Cameroon, at the edge between evergreen and semi-evergreen forests. Data of above-ground woody biomass were obtained from destructive sampling of 138 trees belonging to 47 taxa across a huge range of diameter (5.30–192.50 cm) and wood specific gravity (0.284–1.152 g cm 3). A set of local site-specific multi- and single-species models relating above-ground biomass to tree diameter and wood specific gravity were fitted to the data. The best model was selected using information criterion. Both tree diameter and wood specific gravity were important predictor to consider for the estimation of above-ground biomass at tree scale. Single-species models were not necessarily better than multi-species models including wood specific gravity as a predictor. The best local multi-species model had the same structure and parameters as the pan-tropical equation developed by Chave et al. (2005) for moist forests. The estimates from the pan-tropical multi-species equation were nearly as good as those of the local multi-species equation. Using wood specific gravity from the global data base only slightly increased the estimation errors, because for the study taxa wood specific gravity was highly correlated to wood specific gravity from the global data base. In this study, we showed that the pantropical multi-species allometric equation developped for moist forests can be used to produce accurate estimates of biomass and carbon stocks from diameter measurement in forest inventory and wood specific gravity from global data base at species level. These findings are especially timely given the urgent need to quantify biomass and carbon stocks in the tropics, and given the spatial extent of moist forests in Central Africa. [less ▲]

Volume tables are routinely used by forest planners and managers, but generally with no regard for the conditions in which they are applied (geographical zone, diameter range), which can cause errors in ... [more ▼]

Volume tables are routinely used by forest planners and managers, but generally with no regard for the conditions in which they are applied (geographical zone, diameter range), which can cause errors in estimations of timber volumes. The aim of this study is to test the validity of currently available volume tables, including those used by the government, for three commercial tree species in the forests of south-eastern Cameroon, and if required to propose tables suited to the study zone. The three species concerned are sapelli, Entandrophragma cylindricum, tali, Erythrophleum suaveolens, and assamela Pericopsis elata. Dendrometric data were collected by destructive sampling of 43 trees that were evenly distributed across the diameter range. Stemwood volume was calculated through successive butt-log measurements and linear and non-linear volume tables were adjusted by means of the weighted least-squares method. The results show that the best volume tables for all three species are non-linear. The equations used by the forests authority until now significantly under-estimate standing timber volumes and the estimation errors increase with the size of the trees. The proposed volume tables, once validated, should in future produce more accurate estimations of standing timber in the study zone. Given the international challenges involving Cameroon (FLEGT and REDD+), it is essential that it should have effective tools for estimating standing timber volumes. It is therefore important for Cameroon’s forests authority to conduct a large-scale programme to revise its volume tables. [less ▲]

The division of labour plays a major role in the success of social insects. For instance, through social prophylaxis, the spread of pathogens within the colony can be reduced if corpse removal is the ... [more ▼]

The division of labour plays a major role in the success of social insects. For instance, through social prophylaxis, the spread of pathogens within the colony can be reduced if corpse removal is the concern of a specialized group of ants. However, in relatively small colonies, the number of dead individuals and the amount of waste may be too low to justify a specialized group of corpse carriers. We examined the corpse removal habits of the common red ant, Myrmica rubra. Ants acting as corpse carriers were not strictly specialized in corpse management, but split their time between disposing of the dead and foraging. Some corpse-carrying individuals, however, developed a short-term specialization by making several successive corpse transports. Corpse carriers limited cross-contamination by remaining mostly outside the nest and congregating near the nest entrance when resting inside. [less ▲]

This paper is the first to report data on wildlife-vehicle collisions (WVC) in Wallonia, southern Belgium, characterised by one of the densest road network worldwide. With the collaboration of police we ... [more ▼]

This paper is the first to report data on wildlife-vehicle collisions (WVC) in Wallonia, southern Belgium, characterised by one of the densest road network worldwide. With the collaboration of police we identified 3965 accidents involving “free ranging animal” between 2003 and 2011. We observed that these accidents with free ranging animals result in 13% of cases in injuries for the drivers or passengers, and in less than 1% of cases in fatalities (death). 78% of these casualties involve wild animals, among which wild boar take the largest part (39% ). During the covered period we observed an annual increase of WVC of 21%. For wild boar and red deer, this increase was significantly correlated with hunting statistics, used as an index of population density. The temporal analysis demonstrated an increase of WVC during night time with peak of accidents at dusk and dawn. Monthly distribution revealed the role of breeding, dispersal and hunting in shaping temporal patterns of accidents. Spatial analysis, focusing on wild boar, roe deer, red deer and red fox demonstrated clustering of accidents for all these species, until scale between 20 to 70 km. Mapping of accidents via Kernel density analysis permitted us to highlight areas with high risk of WVC risk. Our study suggests that the problem of car accidents due to wildlife is an increasing concern in Wallonia but results on spatial and temporal patterns should help for setting up mitigation measures in the most sensible areas. Moreover we suggest that police data source should be used for nationwide analysis and for comparison between countries. [less ▲]

Private teak plantations in southern Benin have been established at an increasing rate in the last thirty years. To remedy the lack of reliable information on this resource, a methodological approach was ... [more ▼]

Private teak plantations in southern Benin have been established at an increasing rate in the last thirty years. To remedy the lack of reliable information on this resource, a methodological approach was designed to quantify and characterise private teak plantations and gain a better understanding of the private owners involved in teak production in Benin. The method involves “snowball sampling” among three categories of players: forestry service agents, village chiefs and the owners of teak plantations or their representatives. The data collected are the socio-economic profiles of the owners, an overall description of their plantations and dendrometric characterisations of these plantations. In order to assess its performance, the snowball sampling technique was tested by the quadrant method. Snowball sampling identified 1,002 owners and 861.10 ha of Tectona grandis L.f. plantations. Almost 69 % of the plantations were less than 6 years of age, of which 12.4 % were young plantations and 56.7 % coppice. Stands more than 20 years of age accounted for only a very small proportion of these teak resources (0.2 %). With a very low overall afforestation rate, estimated at 3.58 %, and a snowball sampling detection rate of 68.6%, the total area planted with teak was estimated at 1,255.3 ha, within confidence limits of 1,084.5 ha and 1,574.2 ha. The geodatabase built up during the snowball sampling campaign in the Toffo municipality is clearly a promising start for the development of a network of players involved in teak production. The value of snowball sampling in the context of small-scale sylviculture warrants its application to the other municipalities concerned. [less ▲]

Monitoring of game species populations is necessary to adequately assess culling by hunters in areas where natural large predators are absent. However, game managers have to control several species and ... [more ▼]

Monitoring of game species populations is necessary to adequately assess culling by hunters in areas where natural large predators are absent. However, game managers have to control several species and they often lack of an efficient and convenient survey design method. Monitoring several species at that same time over large areas could thus be cost– and time–effective. We tested the influence of several factors during monitoring of three common game species, (wild boar, roe deer and red fox, using road–based distance sampling in association with thermal imagers. This pilot survey based on 20 night counts in five contrasting sites studied the effect of several covariates (species, thermal imaging, observer, group size, and habitat type) on the detection probabilities. No differences were observed between thermal imagers and group sizes , but we found differences between observers . Expected differences were also observed between species and between habitat type. Our results show that the detectability of low cost thermal imaging equipment is similar to that of more expensive methods, highlighting new possibilities for the use of thermal imagery by game managers. Although adjustments should be made to the study design our findings suggest that large–scale multi–species monitoring could be an efficient method for common game species. [less ▲]

Pericopsis elata (Fabaceae) is a tall tree of high commercial value of the moist semi-deciduous African forests. As a result of logging which started decades ago, it is considered as threatened and ... [more ▼]

Pericopsis elata (Fabaceae) is a tall tree of high commercial value of the moist semi-deciduous African forests. As a result of logging which started decades ago, it is considered as threatened and included on both IUCN Red List and CITES Appendix II even though essential biological parameters controlling its population dynamics remain unknown. This study aims at improving the knowledge of the species ecological parameters and at assessing the impact of selective logging on its populations in an 118,052 ha forest in Cameroon. After inventorying the species in 1,432 ha, mortality and growth were assessed over continuous 5- and 2-year periods in unlogged and logged areas, respectively. Phenology was monitored in the unlogged forest during 5 years. The population structure followed a bell-shaped curve. Mean annual diameter increments in both environments did not differ significantly between unlogged and logged areas. P. elata is a deciduous species that flowers at the end of the main dry season. The minimum reproduction and effective flowering diameters were, respectively, 32 and 37 cm. Fruit maturation took place during 7 months. With a minimum logging diameter of 90 cm, the recovery rate computed over a 30-year period was greater than 100%. Selective logging harvested only 12.1% of the total number of seed trees and had little influence on the species biological parameters. Securing sufficient regeneration as a post-logging action is probably the most important consideration for achieving long-term sustainability. Implications for the conservation status of the species are discussed at the regional level. [less ▲]

With its 4.7 km/km² of public roads, Southern Belgium (Wallonia) has one of the densest road network of Western Europe. This network as well as the observed increase in main game species populations (red ... [more ▼]

With its 4.7 km/km² of public roads, Southern Belgium (Wallonia) has one of the densest road network of Western Europe. This network as well as the observed increase in main game species populations (red deer, roe deer and wild boar) make Wallonia an interesting region for studying the patterns of traffic accidents caused by animals. Moreover, compared to most of European countries, no statistics are available for this area. To shed light on the current situation of wildlife roadkills, the police database of traffic accident statement was thoroughly investigated. Those statements concern accidents that occurred between 2006 and 2010. Each record includes date, time, species involved and information about the location of the accident event. Based on this dataset, we have analysed (i) composition and percentage of involved species, (ii) the consequence (material damages / bodily injuries), (iii) the spatial (type of roads, proximity to landscape features, ‘hot spot’ map) and (iv) temporal (daily, weekly and seasonal) distribution of animal-related accidents. In conclusion future research perspectives are presented. [less ▲]

The arrival of mini-UAV (Unmanned Aerial Vehicle), these small autonomous aircrafts, has opened the doors to a new environmental data acquisition’s approach. In forestry, low-altitude imagery from UAV can ... [more ▼]

The arrival of mini-UAV (Unmanned Aerial Vehicle), these small autonomous aircrafts, has opened the doors to a new environmental data acquisition’s approach. In forestry, low-altitude imagery from UAV can be used to characterize forest ecosystem structure through a Canopy Height Model (CHM). In this research, authors developed a new workflow for acquiring low-altitude aerial images with a mini-UAV and used them for the construction of a high resolution Canopy Height Model. An accuracy analysis is performed and shows that individual dominant tree height can be measured from (UAV-photo-) CHM with a precision of 2 meters. [less ▲]